1. Field of the Invention
This invention relates to a continuous process of producing fatty alcohols by a catalytic hydrogenation of fatty acids or fatty acid derivatives at temperatures of 240.degree. to 330.degree. C. and pressures of 200 to 700 bars in the presence of copper-chromium oxide catalysts, which may be modified by additional components, comprising feeding the feedstock to be hydrogenated into a high pressure chamber, feeding hydrogen and feeding a dispersion of the catalyst into said high pressure chamber equipped with a return pipe, thoroughly mixing the ingredients, causing the reaction to take place in the presence of a large quantity of material which has been almost completely or completely reacted, withdrawing the surplus hydrogen and recycling it to the high pressure chamber, and withdrawing the reaction product.
A thorough mixing and an intense exchange of material are desired in such process, also a high yield of hydrogenated product and a useful life of the catalyst which is used.
2. Discussion of the Prior Art
In an attempt to meet these requirements it has been proposed to produce fatty alcohols continuously by a catalytic hydrogenation of fatty acid or fatty acid derivatives at temperatures of 240.degree. to 330.degree. C. and pressures of 200 to 700 bars in the presence of copper-chromium oxide catalysts, which may be modified by additional components, wherein the feedstock to be hydrogenated is continuously fed into a high pressure chamber, in which a large quantity of material which has been almost completely or completely reacted is thoroughly mixed with the catalyst and the hydrogen (German Pat. No. 1,112,056; U.S. Pat. No. 3,180,898).
In the known process, it is usual to carry out the reaction in a high pressure reactor, in which a return pipe for recycling the completely reacted material is disposed suitably in a central position. Hydrogen is fed and distributed at the lower end of the reactor. The hydrogen supplied in a surplus produces a mammoth pump effect, which causes the catalyst-containing fatty alcohol to rise. When the hydrogen has been separated, the fatty alcohol returns through the return pipe into the lower part (section) of the reactor. Generally, the "lower part" is a part from the bottom of the reactor, which is generally vertical and cylindrical, up to a point one-third of the vessel's height, preferably up to no higher from the bottom than one diameter of the vessel. In order to ensure that the mammoth pump action will be as effective as possible, the upper part (section) of the reactor is provided with suitable means for separating the hydrogen as effectively as possible so that the effect of entrained hydrogen bubbles to decrease the velocity of the return flow is minimized. A catalyst, which is usually mixed with fatty alcohol to form a dispersion, is also fed at the required rate into the reactor cycle. The acid is distributed as uniformly as possible at the lower end of the reactor and mixes with the circulating reaction mixture. The ratio of feedstock to circulating reaction mixture should be at least 1:10, preferably 1:100 to 1:1000. The resulting mixing will result in only a slight damage to the catalyst. Because the fatty acid is mixed with virtually completely reacted material and owing to the presence of surplus hydrogen, which is supplied to the high pressure chamber at a rate which is at least 3 times and suitably 10 to 50 times higher than the rate at which hydrogen is consumed, the fatty acid is rapidly diluted and is most effectively esterified with completely reacted material, consisting mainly of fatty alcohol. The resultant fatty acid-fatty alcohol ester does not attack the catalyst and is hydrogenated in the reaction chamber to form fatty alcohol. Surplus hydrogen leaves the reactor at its top jointly with the reacton water, the fatty alcohol and the catalyst at a rate which depends on the feed rates of fatty acid and catalyst dispersion.
It is an object of the invention to improve the mixing of the circulating material with the fatty acid feedstock so that the attack of acid on the catalyst will be further decreased and the catalyst will be damaged less than even in the process described above. Additionally, it is an object to increase the throughput and/or decrease the catalyst consumption.